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Abstract
The cerebral microcirculation undergoes dynamic changes in parallel with the development of neurons, glia, and their energy metabolism throughout gestation and postnatally. Cerebral blood flow (CBF), oxygen consumption, and glucose consumption are as low as 20% of adult levels in humans born prematurely but eventually exceed adult levels at ages 3 to 11 years, which coincide with the period of continued brain growth, synapse formation, synapse pruning, and myelination. Neurovascular coupling to sensory activation is present but attenuated at birth. By 2 postnatal months, the increase in CBF often is disproportionately smaller than the increase in oxygen consumption, in contrast to the relative hyperemia seen in adults. Vascular smooth muscle myogenic tone increases in parallel with developmental increases in arterial pressure. CBF autoregulatory response to increased arterial pressure is intact at birth but has a more limited range with arterial hypotension. Hypoxia-induced vasodilation in preterm fetal sheep with low oxygen consumption does not sustain cerebral oxygen transport, but the response becomes better developed for sustaining oxygen transport by term. Nitric oxide tonically inhibits vasomotor tone, and glutamate receptor activation can evoke its release in lambs and piglets. In piglets, astrocyte-derived carbon monoxide plays a central role in vasodilation evoked by glutamate, ADP, and seizures, and prostanoids play a large role in endothelial-dependent and hypercapnic vasodilation. Overall, homeostatic mechanisms of CBF regulation in response to arterial pressure, neuronal activity, carbon dioxide, and oxygenation are present at birth but continue to develop postnatally as neurovascular signaling pathways are dynamically altered and integrated. © 2021 American Physiological Society. Compr Physiol 11:1-62, 2021.
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Capellini VK, Restini CBA, Bendhack LM, Evora PRB, Celotto AC. The effect of extracellular pH changes on intracellular pH and nitric oxide concentration in endothelial and smooth muscle cells from rat aorta. PLoS One 2013; 8:e62887. [PMID: 23690964 PMCID: PMC3656859 DOI: 10.1371/journal.pone.0062887] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 03/26/2013] [Indexed: 11/29/2022] Open
Abstract
Aims It has been known for more than a century that pH changes can alter vascular tone. However, there is no consensus about the effects of pH changes on vascular response. In this study, we investigated the effects of extracellular pH (pHo) changes on intracellular pH (pHi) and intracellular nitric oxide concentration ([NO]i) in freshly isolated endothelial cells and cross sections from rat aorta. Main Methods The HCl was used to reduce the pHo from 7.4 to 7.0 and from 7.4 to 6.5; the NaOH was used to increase the pHo from 7.4 to 8.0 and from 7.4 to 8.5. The fluorescent dyes 5-(and-6)-carboxy SNARF-1, acetoxymethyl ester, acetate (SNARF-1) and diaminofluorescein-FM diacetate (DAF-FM DA) were employed to measure the pHi and [NO]i, respectively. The fluorescence intensity was measured in freshly isolated endothelial cells by flow cytometry and in freshly obtained aorta cross sections by confocal microscopy. Key Findings The endothelial and vascular smooth muscle pHi was increased at pHo 8.5. The extracellular acidification did not change the endothelial pHi, but the smooth muscle pHi was reduced at pHo 7.0. At pHo 8.5 and pHo 6.5, the endothelial [NO]i was increased. Both extracellular alkalinization and acidification increased the vascular smooth muscle [NO]i. Significance Not all changes in pHo did result in pHi changes, but disruption of acid-base balance in both directions induced NO synthesis in the endothelium and/or vascular smooth muscle.
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Affiliation(s)
- Verena K. Capellini
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Carolina B. A. Restini
- Laboratory of Pharmacology, Department of Physics and Chemistry, School of Pharmaceutical Science, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Lusiane M. Bendhack
- Laboratory of Pharmacology, Department of Physics and Chemistry, School of Pharmaceutical Science, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Paulo R. B. Evora
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Andréa C. Celotto
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
- * E-mail:
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Knecht KR, Leffler CW. Distinct effects of intravascular and extravascular angiotensin II on cerebrovascular circulation of newborn pigs. Exp Biol Med (Maywood) 2011; 235:1479-88. [PMID: 21127344 DOI: 10.1258/ebm.2010.010149] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Angiotensin II (AngII) is important in regulation of vascular resistance and control of blood flow among organs and tissues. The effect of AngII on the cerebral microvasculature may be mediated or altered by endothelial-derived signals. The aim of this study was to test the hypothesis that blood AngII dilates neonatal pial arterioles via an endothelial-dependent mechanism but brain AngII can constrict pial arterioles by activating smooth muscle AT1 receptors. Studies used anesthetized newborn pigs with surgically implanted closed cranial windows. AngII was given either by infusion into the carotid artery ipsilateral to the cranial window or topically. Intracarotid infusion of AngII dilated pial arterioles. The dilation was blocked by systemic administration of the AT1-receptor antagonist, losartan, but unaffected by topical losartan. Topical AngII also caused dilation, but this dilation was converted to constriction by topical losartan. In piglets pretreated with the angiotensin-converting enzyme (ACE) inhibitor, enalapril, topical AngII constricted, rather than dilated, pial arterioles. In enalapril-treated piglets, light/dye endothelial injury blocked dilation to intracarotid AngII but did not affect constriction to topical AngII. Either indomethacin or l-nitroarginine methyl ester blocked the dilation to intraluminal AngII, but neither affected constriction to topical AngII. Chromium mesoporphyrin, that inhibits heme oxygenase, did not affect responses to either topical or intravascular AngII. These data are consistent with the hypotheses that: (a) circulating AngII dilates pial arterioles via endothelial AT(1) receptor-derived relaxing factors, notably prostanoids and nitric oxide; (b) direct AT(1) receptor activation on the brain side of the blood-brain barrier by AngII causes AT(1) receptor-mediated constriction that can mask underlying AT(1) receptor-independent dilation when ACE is inhibited. Clinical manipulation of the renin-angiotensin system will have disparate actions on cerebral circulation depending on the functional integrity of the intima and ACE.
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Affiliation(s)
- Kenneth R Knecht
- Department of Pediatrics, University of Tennessee Center for the Health Sciences, Memphis, TN 38163, USA
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Toda N, Ayajiki K, Okamura T. Cerebral Blood Flow Regulation by Nitric Oxide: Recent Advances. Pharmacol Rev 2009; 61:62-97. [DOI: 10.1124/pr.108.000547] [Citation(s) in RCA: 268] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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Dani C, Bertini G, Corsini I, Elia S, Vangi V, Pratesi S, Rubaltelli FF. The fate of ductus arteriosus in infants at 23-27 weeks of gestation: from spontaneous closure to ibuprofen resistance. Acta Paediatr 2008; 97:1176-80. [PMID: 18624987 DOI: 10.1111/j.1651-2227.2008.00871.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Some extremely preterm infants experience spontaneous closure of the ductus arteriosus. On the other side, a high percentage (22-30%) of preterm infants born at the lower gestational age fail to respond to a single course of ibuprofen. AIM To assess if there are clinical characteristics effective as predictive factors for spontaneous closure of the ductus arteriosus, development of patent ductus arteriosus (PDA) and ibuprofen-resistant PDA. METHODS A cohort of inborn infants less than 28 weeks of gestation were prospectively studied. We distinguished infants who had spontaneous closure of ductus arteriosus, who developed PDA and who developed ibuprofen-resistant PDA. RESULTS We studied 34 infants. Eight infants (24%) had spontaneous closure of PDA, 17 infants (50%) had a closure of PDA following the first ibuprofen course, while 9 infants (26%) failed to respond to the first ibuprofen course. Infants born at 23-25 weeks of gestation were found to have lower likelihood of PDA spontaneous closure, and higher risk of developing PDA refractory to ibuprofen therapy. Sepsis was found to increase significantly the risk of ibuprofen failure in closing PDA. CONCLUSION An important percentage of extremely preterm infants exhibited spontaneous closure of PDA. Among clinical characteristics lowest gestational ages predict PDA and ibuprofen-resistant PDA, while sepsis predicts only ibuprofen-resistant PDA.
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MESH Headings
- Blood Coagulation/drug effects
- Cyclooxygenase Inhibitors/administration & dosage
- Dose-Response Relationship, Drug
- Drug Resistance
- Ductus Arteriosus/diagnostic imaging
- Ductus Arteriosus/physiology
- Ductus Arteriosus, Patent/complications
- Ductus Arteriosus, Patent/diagnostic imaging
- Ductus Arteriosus, Patent/drug therapy
- Ductus Arteriosus, Patent/surgery
- Echocardiography, Doppler
- Humans
- Ibuprofen/administration & dosage
- Ibuprofen/adverse effects
- Ibuprofen/pharmacology
- Infant, Newborn
- Infant, Premature/physiology
- Kidney/drug effects
- Logistic Models
- Prospective Studies
- Respiration, Artificial
- Respiratory Distress Syndrome, Newborn/complications
- Respiratory Distress Syndrome, Newborn/diagnosis
- Respiratory Distress Syndrome, Newborn/therapy
- Treatment Outcome
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Affiliation(s)
- Carlo Dani
- Department of Surgical and Medical Critical Care, Section of Neonatology, Careggi University Hospital of Florence, Florence, Italy.
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Sodini D, Baragatti B, Barogi S, Laubach VE, Coceani F. Indomethacin promotes nitric oxide function in the ductus arteriosus in the mouse. Br J Pharmacol 2008; 153:1631-40. [PMID: 18297107 PMCID: PMC2438253 DOI: 10.1038/bjp.2008.36] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Accepted: 01/15/2008] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE Prenatal patency of ductus arteriosus is maintained by prostaglandin (PG) E(2) in concert with nitric oxide (NO) and carbon monoxide (CO). Accordingly, we have previously found that NO activity increases upon deletion of either COX. Here, we have examined whether COX inhibition by indomethacin mimics COX deletion in promoting NO. EXPERIMENTAL APPROACH Experiments were performed in vitro and in vivo with wild-type (WT) and eNOS-/-, near-term mouse foetuses. Indomethacin was given p.o. to the mother as single (acute treatment) or repeated (daily for 3 days; chronic treatment) doses within a therapeutic range (2 mg kg(-1)). KEY RESULTS Indomethacin promoted eNOS mRNA expression in the WT ductus. Coincidentally, the drug enhanced the contraction of the isolated ductus to the NOS inhibitor, N(G)-nitro-L-arginine methyl ester, and its effect augmented with the length of treatment. No such enhancement was seen with the eNOS-/- ductus. Chronic indomethacin also increased, albeit marginally, the contraction of the WT ductus to the CO synthesis inhibitor, zinc protoporphyrin. Whether given acutely or chronically, indomethacin induced a little narrowing of the ductus antenatally and had no effect on postnatal closure of the vessel. CONCLUSIONS AND IMPLICATIONS We conclude that activation of NO and, to a much lesser degree, CO mechanisms is an integral part of the indomethacin effect on the ductus. This relaxing influence may oppose the contraction from PGE(2) suppression and could explain the failures of indomethacin therapy in premature infants with persistent duct.
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Affiliation(s)
- D Sodini
- Scuola Superiore Sant'Anna Pisa, Italy
| | - B Baragatti
- Scuola Superiore Sant'Anna Pisa, Italy
- Institute of Clinical Physiology CNR Pisa, Italy
| | - S Barogi
- Scuola Superiore Sant'Anna Pisa, Italy
- Institute of Clinical Physiology CNR Pisa, Italy
| | - V E Laubach
- Department of Surgery, University of Virginia Health System Charlottesville, VA, USA
| | - F Coceani
- Scuola Superiore Sant'Anna Pisa, Italy
- Institute of Clinical Physiology CNR Pisa, Italy
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Kanu A, Whitfield J, Leffler CW. Carbon monoxide contributes to hypotension-induced cerebrovascular vasodilation in piglets. Am J Physiol Heart Circ Physiol 2006; 291:H2409-14. [PMID: 16751286 PMCID: PMC1593219 DOI: 10.1152/ajpheart.01368.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The gaseous compound carbon monoxide (CO) has been identified as an important endogenous biological messenger in brain and is a major component in regulation of cerebrovascular circulation in newborns. CO is produced endogenously by catabolism of heme to CO, free iron, and biliverdin during enzymatic degradation of heme by heme oxygenase (HO). The present study was designed to test the hypothesis that endogenously produced CO contributes to hypotension-induced vasodilation of cerebral arterioles. Experiments used anesthetized piglets with implanted, closed cranial windows. Topical application of the HO substrate heme-l-lysinate caused dilation of pial arterioles that was blocked by a metal porphyrin inhibitor of HO, chromium mesoporphyrin (CrMP). In normotensive piglets (arterial pressure 64 +/- 4 mmHg), CrMP did not cause vasoconstriction of pial arterioles but rather a transient dilation. Hypotension (50% of basal blood pressure) increased cerebral CO production and dilated pial arterioles from 66 +/- 2 to 92 +/- 7 microm. In hypotensive piglets, topical CrMP or intravenous tin protoporphyrin decreased cerebral CO production and produced pial arteriolar constriction to normotensive diameters. In additional experiments, because prostacyclin and nitric oxide (NO) are also key dilators that can contribute to cerebrovascular dilation, we held their levels constant. NO/prostacyclin clamp was accomplished with continuous, simultaneous application of indomethacin, N(omega)-nitro-l-arginine, and minimal dilatory concentrations of iloprost and sodium nitroprusside. With constant NO and prostacyclin, the transient dilator and prolonged constrictor responses to CrMP of normotensive and hypotensive piglets, respectively, were the same as when NO and prostaglandins were not held constant. These data suggest that endogenously produced CO contributes to cerebrovascular dilation in response to reduced perfusion pressure.
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Affiliation(s)
- Alie Kanu
- Dept. of Physiology, Univ. of Tennessee Health Science Center, 894 Union Ave, Memphis, TN 38163, USA
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Ray CJ, Marshall JM. The cellular mechanisms by which adenosine evokes release of nitric oxide from rat aortic endothelium. J Physiol 2005; 570:85-96. [PMID: 16239264 PMCID: PMC1464284 DOI: 10.1113/jphysiol.2005.099390] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Adenosine and nitric oxide (NO) are important local mediators of vasodilatation. The aim of this study was to elucidate the mechanisms underlying adenosine receptor-mediated NO release from the endothelium. In studies on freshly excised rat aorta, second-messenger systems were pharmacologically modulated by appropriate antagonists while a NO-sensitive electrode was used to measure adenosine-evoked NO release from the endothelium. We showed that A1-mediated NO release requires extracellular Ca2+, phospholipase A2 (PLA2) and ATP-sensitive K+ (KATP) channel activation whereas A2A-mediated NO release requires extracellular Ca2+ and Ca2+-activated K+ (KCa) channels. Since our previous study showed that A1- and A2A-receptor-mediated NO release requires activation of adenylate cyclase (AC), we propose the following novel pathways. The K+ efflux resulting from A1-receptor-coupled KATP-channel activation facilitates Ca2+ influx which may cause some stimulation of endothelial NO synthase (eNOS). However, the increase in [Ca2+]i also stimulates PLA2 to liberate arachidonic acid and stimulate cyclooxygenase to generate prostacyclin (PGI2). PGI2 acts on its endothelial receptors to increase cAMP, so activating protein kinase A (PKA) to phosphorylate and activate eNOS resulting in NO release. By contrast, the K+ efflux resulting from A2A-coupled KCa channels facilitates Ca2+ influx, thereby activating eNOS and NO release. This process may be facilitated by phosphorylation of eNOS by PKA via the action of A2A-receptor-mediated stimulation of AC increasing cAMP. These pathways may be important in mediating vasodilatation during exercise and systemic hypoxia when adenosine acting in an endothelium- and NO-dependent manner has been shown to be important.
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Affiliation(s)
- Clare J Ray
- Department of Physiology, The Medical School, University of Birmingham, Birmingham B15 2TT, UK.
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White CR, Hamade MW, Siami K, Chang MM, Mangalwadi A, Frangos JA, Pearce WJ. Maturation enhances fluid shear-induced activation of eNOS in perfused ovine carotid arteries. Am J Physiol Heart Circ Physiol 2005; 289:H2220-7. [PMID: 15923310 DOI: 10.1152/ajpheart.01013.2004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study tests the hypothesis that age-dependent increases in endothelial vasodilator capacity are due to maturational increases in endothelial nitric oxide (NO) synthesis and release. Intact 4-cm carotid artery segments taken from term fetal lambs and nonpregnant adult sheep were perfused by using a closed system that enabled independent control of flow and inflow pressure and facilitated complete recovery of all NO released. Fluid shear stress induced a graded release of NO (in nmol NO x min x cm(-2) of luminal surface area) that was significantly greater in adult (890 +/- 140) than in fetal (300 +/- 40) carotid arteries at corresponding values of shear stress (5.9 +/- 0.3 dyn/cm2) but was independent of inflow pressure in both age groups. These age-related differences in NO release were not attributable to corresponding differences in endothelial NO synthase (eNOS) abundance, as eNOS protein levels (in ng of eNOS/cm2 of luminal surface area) were similar in adult (14 +/- 2) and fetal (12 +/- 1) arteries. Adult (80 +/- 15) and fetal (89 +/- 32) levels of eNOS mRNA (in 10(6) copies/cm2 of luminal surface area) were also similar. However, when NO release was normalized relative to the associated mass of eNOS protein to estimate eNOS-specific activity in situ, this value (in nmol NO x microg of eNOS(-1) x min(-1)) was significantly greater in adult (177 +/- 44) than in fetal (97 +/- 36) arteries when the endothelium was maximally activated by A-23187. Similarly, the slope of the relation between fluid shear stress and estimated eNOS-specific activity (in nmol NO x microg of eNOS(-1) x min(-1) per dyn/cm2) was also significantly greater in adult (6.8 +/- 0.1) than in fetal (2.9 +/- 0.1) arteries, which suggests that eNOS may be more sensitive to or more efficiently coupled to activating stimuli in adult compared with fetal arteries. We conclude that maturational increases in endothelial vasodilator capacity are attributable to age-dependent increases in NO release secondary to elevated eNOS-specific activity and involve more efficient coupling between endothelial activation and enhancement of eNOS activity in adult compared with fetal arteries.
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Affiliation(s)
- Charles Ray White
- Center for Perinatal Biology, Loma Linda Univ., Loma Linda, CA 92350, USA
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Gaber MW, Yuan H, Killmar JT, Naimark MD, Kiani MF, Merchant TE. An intravital microscopy study of radiation-induced changes in permeability and leukocyte–endothelial cell interactions in the microvessels of the rat pia mater and cremaster muscle. ACTA ACUST UNITED AC 2004; 13:1-10. [PMID: 15063835 DOI: 10.1016/j.brainresprot.2003.11.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/25/2003] [Indexed: 11/18/2022]
Abstract
Using intravital microscopy and a closed window method, we measured irradiation-induced changes in the vascular permeability and cell interactions in microcirculation networks of the rat pia mater; the same effects were monitored in the cremaster muscle as a control. The closed cranial window has many advantages, including long-term direct visualization of microcirculation. The method allows for repeated testing of the same vessel or network, thereby reducing variability. The method also allows for measurement of permeability changes and the accompanying leukocyte-endothelial cell interactions in the same network or vessel, which permits correlative studies of these phenomena. However, this method is not without challenges. The optical conditions are difficult, because the brain is three-dimensional and its parenchyma is more complex than the thinner, flatter peripheral tissues. To overcome this limitation, we performed a dynamic background subtraction. The background is dynamically related to vessel intensity, and changes in intensity were determined by eliminating the effects of neighboring and underlying vessels. We applied this method to studying the effects of ionizing radiation on the blood-brain barrier (BBB) permeability and cell interactions and the modulation of these effects by anti-ICAM-1 antibodies. Our results demonstrate that this method is sensitive to changes in these properties of the BBB.
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Affiliation(s)
- M Waleed Gaber
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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Affiliation(s)
- Holger Scholz
- Johannes-Müller-Institut für Physiologie, Humboldt-Universität, Charité, Tucholskystrasse 2, 10117 Berlin, Germany.
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Baragatti B, Brizzi F, Ackerley C, Barogi S, Ballou LR, Coceani F. Cyclooxygenase-1 and cyclooxygenase-2 in the mouse ductus arteriosus: individual activity and functional coupling with nitric oxide synthase. Br J Pharmacol 2003; 139:1505-15. [PMID: 12922938 PMCID: PMC1573985 DOI: 10.1038/sj.bjp.0705391] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2003] [Revised: 05/19/2003] [Accepted: 05/20/2003] [Indexed: 11/09/2022] Open
Abstract
1. Prenatal patency of the ductus arteriosus is maintained by prostaglandin (PG) E(2), conceivably in concert with nitric oxide (NO). Local PGE(2) formation is sustained by cyclooxygenase-1 (COX1) and cyclooxygenase-2 (COX2), a possible exception being the mouse in which COX1, or both COXs, are reportedly absent. Here, we have examined the occurrence of functional COX isoforms in the near-term mouse ductus and the possibility of COX deletion causing NO upregulation. 2. COX1 and COX2 were detected in smooth muscle cells by immunogold electronmicroscopy, both being located primarily in the perinuclear region. Cytosolic and microsomal PGE synthases (cPGES and mPGES) were also found, but they occurred diffusely across the cytosol. COX1 and, far more frequently, COX2 were colocalised with mPGES, while neither COX appeared to be colocalized with cPGES. 3. The isolated ductus from wild-type and COX1-/- mice contracted promptly to indomethacin (2.8 micro M). Conversely, the contraction of COX2-/- ductus to the same inhibitor started only after a delay and was slower. 4. N(G)-nitro-L-arginine methyl ester (L-NAME, 100 micro M) weakly contracted the isolated wild-type ductus. Its effect, however, increased three- to four-fold after deleting either COX, hence equalling that of indomethacin. 5. In vivo, the ductus was patent in all mice foetuses, whether wild-type or COX-deleted. Likewise, no genotype-related difference was noted in its postnatal closure. 6. We conclude that the mouse ductus has a complete system for PGE(2) synthesis comprising both COX1 and COX2. The two enzymes respond differently to indomethacin but, nevertheless, deletion of either one results in NO upregulation. PGE(2) and NO can function synergistically in keeping the ductus patent.
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Affiliation(s)
- B Baragatti
- Institute of Clinical Physiology CNR, 56127 Pisa, Italy
| | - F Brizzi
- Scuola Superiore S. Anna, 56127 Pisa, Italy
| | - C Ackerley
- Department of Pathology, Hospital for Sick Children, Toronto, Ontario, Canada, M5G 1X8
| | - S Barogi
- Institute of Clinical Physiology CNR, 56127 Pisa, Italy
| | - L R Ballou
- Departments of Medicine and Molecular Sciences, University of Tennessee/Department of Veterans Affairs, Memphis, TN 38104, U.S.A
| | - F Coceani
- Institute of Clinical Physiology CNR, 56127 Pisa, Italy
- Scuola Superiore S. Anna, 56127 Pisa, Italy
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